Re: [Haskell-cafe] There is no null; Maybe/Option types

22 Apr 2011


      On Fri, 22 Apr 2011, Maciej Marcin Piechotka wrote:
...
On Fri, 2011-04-22 at 21:26 +0200, Henning Thielemann wrote:
...
In idiomatic Haskell you would write
case userList of
    Nothing -> Nothing
    Just plainUserList =
       let user = findUser "bob" plainUserList
       ...
since (userList /= Nothing) requires an Eq instance without need and it
requires fromJust. Or was there an educational purpose to write it with
(/= Nothing) ?
Using 'more advanced haskell'
email = getEmail =<< findUser "bob" =<< userList
This is what Christopher Done wrote some lines below the code, that I 
quoted.